UK electricity companies are preparing for the introduction Of new standards of quality of supply by the Industry Regulator From April 2002 financial penalties will be imposed relating to multiple interruptions. This article reviews some of the statistical factors affecting the number of such interruptions. Circuit reliability analysis based on average fault rates is used to estimate average customer interruptions. A simple statistical model is introduced to provide estimates of the probability of exceeding a specified number of interruptions per annum. This is illustrated by reference to a group of HV circuits.